The instant invention relates to easy open end closure members for containers and the like. More particularly, it is concerned with providing a depressible tab for can end closures that includes a nose portion wherein an improved pressure relief means in the form of a unique vent notch is incorporated in the nose structure of the tab.
Significant problems involved in the construction and use of depressible or push button tabs for beer and effervescent beverage containers and the like concern the controlled relief of internal pressures and the venting of the individual container's contents to the atmosphere during initial opening of the can or container equipped with such tabs so as to avoid undesirable outward spraying and splattering, frothing and foaming of the container's contents.
In an attempt to avoid the aforesaid problems it has been proposed in the past to use a pair of differentially sized openings in a can top which are covered by depressible push buttons, the smaller opening and its associated push button comprising a pressure release and vent opening and the larger opening comprising the pouring opening. The smaller push button is adapted to be opened first because it requires less force. This type of prior art push button or depressible tab container end is illustrated, for example, in U.S. Pat. Nos. 3,902,627; 3,958,717; 3,972,445; 4,033,275; Design Pat. Nos. 226,171 and 233,137 and British Patent Specifications Nos. 1,357,468 of June 19, 1954, and 1,407,806 of Sept. 5, 1975.
It has also been suggested that such prior art small vent openings be incorporated in the principal or large depressible tab structure of an easy open can as evidenced, for example, by the teachings of U.S. Pat. Nos. 3,741,432 and 3,794,206 as well as German Offenlegungsschrift No. 2,421,314 published Nov. 14, 1974. In these instances the smaller depressible tab is adapted to be hingedly connected to the main or larger depressible tab of which it forms a part.